Abstract

One of the most common methods of coupling capillary gas chromatography
(GC) columns to mass spectrometers is the open split interface first described by
Henneberg et al. These devices usually employ a capillary restrictor tube which
governs the amount of gas allowed into the mass spectrometer, with provision for
venting any excess gas to atmosphere or a second detector. There is also usually
provision for one or two "make-up" or "purge" gas lines to supplement column flow
where necessary, to sweep dead volumes within the interface and to enable "cutting" of
large GC peaks away from the mass spectrometer to avoid contamination. Under
these conditions the column exit is at atmospheric pressure and hence combined
GC-mass spectrometry (MS) results can be directly compared with those from normal
GC, since no change in retention times or resolution will have occurred for the same
flow-rates. These interfaces also facilitate the rapid exchange of columns as the mass
spectrometer is not directly exposed to atmospheric pressure, and enable columns
requiring relatively high flow-rates to be used in conjunction with mass spectrometers
of limited pumping capacity.